Spinal column retaining apparatus

ABSTRACT

An apparatus for retaining first and second vertebrae of a spinal column in a desired spatial relationship includes a longitudinal member positionable along the spinal column. A member, such as a plate, connectable with the first vertebra has first and second fastener openings and a portion engageable with the longitudinal member. A first fastener extendable through the first fastener opening in the member has a first end portion for attachment to the first vertebra and has a longitudinal axis. A second fastener extendable through the second fastener opening in the member has a first end portion for attachment to the first vertebra and has a longitudinal axis. The longitudinal axes of the first and second fasteners converge at an acute angle as viewed in a sagittal plane when the first and second fasteners connect the member with the first vertebra. The member connectable with the first vertebra has a body portion and has a lip portion projecting from the body portion of the member. The lip portion of the member is engageable with a surface of the first vertebra facing toward the second vertebra.

This application is a continuation of co-pending application Ser. No.09/655,851, filed on Aug. 31, 1996, now U.S. Pat. No. 5,800,433.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to an apparatus for use in retainingvertebrae of a spinal column in a desired spatial relationship. Inparticular, the present invention relates to an apparatus for use inretaining cervical vertebrae of a human spinal column in a desiredspatial relationship.

2. Description of the Prior Art

There are various known devices for retaining vertebrae of a spinalcolumn in a desired spatial relationship. Certain of such known devicesinclude rods connected to and extending between vertebrae and certain ofsuch known devices include plates connected to and extending betweenvertebrae.

SUMMARY OF THE INVENTION

The present invention is an apparatus for retaining first and secondvertebrae of a spinal column in a desired spatial relationship. Theapparatus includes a longitudinal member positionable along the spinalcolumn. A member connectable with the first vertebra has first andsecond fastener openings and a portion engageable with the longitudinalmember. A first fastener is extendable through the first fasteneropening in the member to connect the member with the first vertebra. Thefirst fastener has a first end portion for attachment to the firstvertebra and has a longitudinal axis. A second fastener is extendablethrough the second fastener opening in the member to connect the memberwith the first vertebra. The second fastener has a first end portion forattachment to the first vertebra and has a longitudinal axis.

In accordance with one feature of the present invention, thelongitudinal axis of the first fastener and the longitudinal axis of thesecond fastener converge at an acute angle as viewed in the sagittalplane when the first and second fasteners connect the member with thefirst vertebra. The apparatus also includes means for connecting thelongitudinal member with the second vertebra.

In accordance with another feature of the present invention, the memberconnectable with the first vertebra has a body portion. The member alsohas a lip portion projecting in a first direction from the body portionof the member. The lip portion of the member is engageable with asurface of the first vertebra facing toward the second vertebra.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features of the present invention will becomemore apparent to one skilled in the art upon reading the followingdescription with reference to the accompanying drawings, wherein:

FIG. 1 is an elevational view of an apparatus constructed in accordancewith the present invention for maintaining a desired spatialrelationship between cervical vertebrae of a spinal column;

FIG. 2 is a view of the apparatus of FIG. 1, taken along the sagittalplane as indicated by line 2—2 of FIG. 1;

FIG. 3 is a sectional view taken generally along line 3—3 of FIG. 2;

FIG. 4 is a sectional view taken generally along line 4—4 of FIG. 2;

FIG. 5 is a perspective view of a first plate which forms a portion ofthe apparatus of FIG. 1;

FIG. 6 is another perspective view of the plate of FIG. 5;

FIG. 7 is a view similar to FIG. 5 of a second plate which forms aportion of the apparatus of FIG. 1;

FIG. 8 is another perspective view of the plate of FIG. 7;

FIG. 9 is a view similar to FIG. 1 of a modified embodiment of theinvention.

FIG. 10 is a perspective view of a plate which is constructed inaccordance with a second embodiment of the present invention; and

FIG. 11 is an enlarged sectional view of a portion of the plate of FIG.10 and showing a set screw and rod associated with the plate;

DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention relates to an apparatus for use in retainingvertebrae of a spinal column in a desired spatial relationship. Asrepresentative of the present invention, FIG. 1 illustrates an apparatus10 for use in retaining bone portions such as cervical vertebrae V1 andV2 of a human spinal column C in a desired spatial relationship. Thespinal column C has an axis A which is a vertical axis of the humanbody.

The apparatus 10 includes a pair of surgically implantable rods 12 and14 (FIGS. 1 and 2). The apparatus 10 also includes first and secondmembers or plates 30 and 32 which engage the rods 12 and 14; threefasteners 38, 40, and 42 for connecting the first plate with the firstvertebra V1; and three fasteners 44, 46, and 48 for connecting thesecond plate with the second vertebra V2.

The first rod 12 (FIG. 1) is made of a suitable biocompatible material,such as titanium or stainless steel. The first rod 12 has an elongatecylindrical configuration and has a circular cross section taken in aplane extending perpendicular to the longitudinal central axis of thefirst rod. The first rod 12 has a smooth outer surface. A first endportion of the first rod 12 is formed as a cap 50. The first rod 12 alsohas a second end portion 52 opposite from the first end portion 50.

The second rod 14 is identical to the first rod 12. The second rod 14has a first end portion which is formed as a cap 54. The second rod 14also has a second end portion 56 opposite from the first end portion 54.The rods 12 and 14 are bendable to a desired configuration to conform toa desired curvature of the spinal column C. The rods 12 and 14 togetherhave sufficient strength and rigidity to maintain the vertebrae V1 andV2 in a desired spatial relationship.

The rods 12 and 14 have a length which is sufficient to enable the rodsto span at least the two vertebrae V1 and V2. The length of the rods 12and 14 will depend upon the condition to be corrected and the number ofvertebrae to be held in a desired spatial relationship relative to eachother by the apparatus 10. If more than two vertebrae are to be held ina desired spatial relationship relative to each other by the apparatus10, the rods 12 and 14 would be longer and more than two plates, such asthe plates 30 and 32, may be used.

The first plate 30 (FIGS. 5 and 6) is made of a suitable biocompatiblematerial, such as titanium or stainless steel. The first plate 30includes a main body portion 60. The main body portion 60 of the firstplate 30 has a planar outer side surface 62 for facing anteriorly oraway from the first vertebra V1. The first plate 30 has an arcuate innerside surface 64 for facing posteriorly or toward the first vertebra V1.The inner side surface 64 of the first plate 30 may engage the anteriorsurface of the first vertebra V1 when the first plate is connected withthe first vertebra as described below.

The main body portion 60 of the first plate 30 has a central portion 66which extends laterally between a first side portion 68 and a secondside portion 70 of the first plate. Because the inner side surface 64 ofthe first plate 30 has an arcuate configuration, the central portion 66of the first plate is relatively thin (as viewed in a direction fromleft to right in FIG. 3) as compared to the first side portion 68 and tothe second side portion 70.

The main body portion 60 of the first plate 30 also has first and secondend portions 72 and 74. The first end portion 72 of the first plate 30includes a planar first end surface 76 of the first plate 30. The secondend portion 74 includes a planar second end surface 78 of the firstplate 30. The second end surface 78 extends parallel to the first endsurface 76.

A first rod passage 80 is formed in the first side portion 68 of thefirst plate 30. The first rod passage 80 is an opening which extendsbetween the first and second end surfaces 76 and 78 of the first plate30 in a direction parallel to the planar outer side surface 62 of thefirst plate. The first rod passage 80 is defined by a cylindricalsurface 81 and tapered pilot surfaces 83 and 84 at opposite ends of thecylindrical surface 81. The diameter of the cylindrical surface 81 isslightly greater than the diameter of the first rod 12, so that thefirst rod and the first plate 30 can be relatively movable.

The second side portion 70 of the first plate 30 is a mirror image ofthe first side portion 68. A second rod passage 82 is formed in thesecond side portion 70 of the first plate 30. The second rod passage 82is an opening which extends between the first and second end surfaces 76and 78 of the first plate 30 in a direction parallel to the planar outerside surface 62 of the first plate. The second rod passage 82 extendsparallel to the first rod passage 80. The second rod passage 82 isdefined by a cylindrical surface 85 and tapered pilot surfaces 86 and 87at opposite ends of the cylindrical surface 85. The diameter of thesecond rod passage 82 is the same as the diameter of the first rodpassage 80. The diameter of the cylindrical surface 85 is slightlygreater than the diameter of the second rod 14, so that the second rodand the first plate 30 can be relatively movable.

A circular first fastener opening 90 extends through the central portion66 of the first plate 30. The first fastener opening 90 has an axis 92(FIG. 2) which extends perpendicular to the plane of the outer sidesurface 62 of the first plate 30. The axis 92 extends in a firstdirection as indicated by the arrow 94, that is, from right to left asviewed in FIG. 2, when the first plate 30 is mounted on the firstvertebra V1. The first direction 94 extends perpendicular to the axes ofthe rods 12 and 14.

The first fastener opening 90 is partially defined by a larger diametercylindrical surface 96 (FIG. 6) which extends from the outer sidesurface 62 of the first plate 30 in a direction into the material of thecentral portion 66 of the first plate. The cylindrical surface 96 iscentered on the axis 92 of the first fastener opening 90. The firstfastener opening 90 is partially defined by a smaller diametercylindrical surface 98 which extends from the inner side surface 64 ofthe first plate 30 in a direction into the material of the centralportion 66 of the first plate to a location spaced radially inward fromthe surface 96. The cylindrical surface 98 is centered on the axis 92 ofthe first fastener opening 90.

An annular shoulder surface 100 (FIGS. 2 and 6) extends radially(relative to the axis 92) between the cylindrical surfaces 96 and 98.The shoulder surface 100 and the larger diameter cylindrical surface 96define a recess 102 in the outer side surface 62 of the first plate 30.

The main body portion 60 of the first plate 30 also includes a circularsecond fastener opening 110 formed at a location adjacent to, but spacedapart from, the first rod passage 80 in the first side portion 68 of thefirst plate. The second fastener opening 110 extends through both thesecond end surface 78 of the first plate 30 and the outer side surface62 of the first plate.

The second fastener opening 110 is partially defined by a largerdiameter cylindrical surface 112 (FIG. 6) which extends from the outerside surface of the first plate 30 in a direction into the material ofthe first side portion 68 of the first plate. The cylindrical surface112 is centered on an axis 114 (FIG. 2) of the second fastener opening110. The cylindrical surface 112 is spaced apart from the first rodpassage 80.

The second fastener opening 110 is partially defined by a smallerdiameter cylindrical surface 116 (FIG. 6) which extends from the innerside surface 64 of the first plate 30 in a direction into the materialof the first side portion 68 of the first plate, to a location spacedradially inward from the surface 112. The cylindrical surface 116 iscentered on the axis 114 of the second fastener opening 110.

An annular shoulder surface 118 (FIGS. 3 and 6) extends radially(relative to the axis 114) between the cylindrical surfaces 112 and 116.The shoulder surface 118 and the larger diameter cylindrical surface 112define a recess 120 in the outer side surface 62 of the first plate 30.

The axis 114 of the second fastener opening 110 extends transverse tothe axis 92 of the first fastener opening 90. Specifically, the axis 114(FIG. 3) of the second fastener opening 110 converges with the axis 92of the first fastener opening 90 as viewed in a transverse plane atright angles to the vertical axis A, as can be seen from FIG. 3. In theillustrated embodiment, the axis 114 converges at an angle of about 100with the axis 92 as viewed in this transverse plane.

The axis 114 of the second fastener opening 110 also converges with theaxis 92 of the first fastener opening 90 as viewed in the sagittalplane, as can be seen in FIG. 2. In the illustrated embodiment, the axis114 converges at an angle of 45° with the axis 92 as viewed in thesagittal plane. It is contemplated that the angle of convergence asviewed in the sagittal plane could be in the range of from about 30° toabout 60°.

The main body portion 60 of the first plate 30 also includes a circularthird fastener opening 130 formed at a location adjacent to, but spacedapart from, the second rod passage 82 in the second side portion 70 ofthe first plate. The third fastener opening 130 extends through both thesecond end surface 78 of the first plate 30 and the outer side surface62 of the first plate.

The third fastener opening 130 is partially defined by a larger diametercylindrical surface 132 (FIG. 6) which extends from the outer sidesurface 62 of the first plate 30 in a direction into the material of thesecond side portion 70 of the first plate. The cylindrical surface 132is centered on an axis 134 (FIG. 4) of the third fastener opening 130.The cylindrical surface 132 is spaced apart from the second rod passage82.

The third fastener opening 130 is partially defined by a smallerdiameter cylindrical surface 136 (FIG. 6) which extends from the innerside surface 64 of the first plate 30 in a direction into the materialof the second side portion 70 of the first plate, to a location spacedradially inward from the surface 32. The cylindrical surface 136 iscentered on the axis 134 of the third fastener opening 130.

An annular shoulder surface 138 (FIGS. 3 and 6) extends radially(relative to the axis 134) between the cylindrical surfaces 132 and 136.The shoulder surface 138 and the larger diameter cylindrical surface 132define a recess 140 in the outer side surface 62 of the first plate 30.

The axis 134 (FIG. 3) of the third fastener opening 130 is coplanar withthe axis 114 of the second fastener opening 110. The axis 134 of thethird fastener opening 130 extends transverse to the axis 92 of thefirst fastener opening 90. Specifically, the axis 134 of the thirdfastener opening 130 converges with the axis 92 of the first fasteneropening 90 as viewed in a transverse plane at right angles to thevertical axis A, as can be seen from FIG. 3. In the illustratedembodiment, the axis 134 converges with the axis 92 at an angle of 10°as viewed in this transverse plane.

The axis 134 of the third fastener opening 130 also converges with theaxis 92 of the first fastener opening 90 as viewed in the sagittalplane, as can be seen from FIG. 2. In the illustrated embodiment, theaxis 134 converges with the axis 92 at an angle of 45° as viewed in thesagittal plane. It is contemplated that this angle of convergence asviewed in the sagittal plane could be in the range of from about 30° toabout 60°.

The first plate 30 includes a lip portion or lip 150 which is formed asone piece with the main body portion 60 of the first plate. The lip 150,best seen in FIGS. 2 and 5, projects from the second end portion 74 ofthe main body portion 60 of the first plate 30. The lip 150 projects inthe first direction 94 (FIG. 2) when the first plate 30 is mounted onthe first vertebra V1.

The lip 150 has a planar configuration as viewed in the first direction94, for example, as seen in FIG. 2. The lip 150 has an arcuateconfiguration, as can be seen in FIG. 5, when viewed in a directionparallel to the plane of the outer side surface 62 of the first plate30. The arcuate configuration of the lip 150 generally follows thearcuate configuration of the inner side surface 64 of the main bodyportion 60 of the first plate 30. The lip 150 extends continuouslybetween the first and second side portions 68 and 70 of the first plate30. Alternatively, the lip 150 may be discontinuous at one or morelocations along the width of the plate 30.

The lip 150 has an outer end surface 152 (FIG. 2) which is formed as anextension of the second end surface 78 of the main body portion 60 ofthe first plate 30. An opposite inner end surface 154 (FIGS. 2 and 5) ofthe lip 150 extends parallel to the outer end surface 152. The lip 150also has an inner side surface 156 which extends between the inner andouter end surfaces 154 and 152 of the lip 150.

The second and third fastener openings 110 and 130 extend partiallythrough the lip 150. The second fastener opening 110, as can be seen inFIG. 2, extends through the corner between, or intersection of, the lip150 and the main body portion 60 of the first plate 30. The thirdfastener opening 130 also extends through the corner between, orintersection of, the lip 150 and the main body portion 60 of the firstplate 30.

The second plate 32 (FIG. 7) is generally similar in configuration tothe first plate 30 (FIG. 5). The second plate 32 (FIG. 7) is configured,however, so that the head ends of fasteners received in certain fasteneropenings in the second plate are engageable with the rods 12 and 14disposed in rod passages in the second plate. This engagement can blockmovement of the second plate 32 relative to the rods 12 and 14, in amanner described below.

The second plate 32 includes a main body portion 160 which has a planarouter side surface 162 for facing anteriorly or away from the vertebraV2. The main body portion 160 also has an arcuate inner side surface 164for facing posteriorly or toward the second vertebra V2. The inner sidesurface 164 of the second plate 32 may engage the anterior surface ofthe second vertebra V2 when the second plate is connected with thesecond vertebra as described below.

The main body portion 160 has a central portion 166 which extendslaterally between a first side portion 168 and a second side portion 170of the second plate 32. Because the inner side surface 164 of the secondplate 32 has an arcuate configuration, the central portion 166 of thesecond plate 32 is relatively thin (as viewed in a direction from leftto right in FIG. 4) as compared to the first side portion 168 and to thesecond side portion 170.

The main body portion 160 of the second plate 32 also has first andsecond end portions 172 and 174. The first end portion 172 of the secondplate 32 includes a planar first end surface 176 of the second plate.The second end portion 174 of the second plate 32 includes a planarsecond end surface 178 of the second plate. The second end surface 178extends parallel to the first end surface 176.

A first rod passage 180 is formed in the first side portion 168 of thesecond plate 32. The first rod passage 180 is an opening which extendsbetween the first and second end surfaces 176 and 178 in a directionparallel to the planar outer side surface 162 of the second plate 32.The first rod passage 180 is defined by a cylindrical surface 181 andtapered pilot surfaces 183 and 184 at opposite ends of the cylindricalsurface 181. The diameter of the cylindrical surface 181 is slightlygreater than the diameter of the first rod 12.

A second rod passage 182 is formed in the second side portion 170 of thesecond plate 32. The second rod passage 182 is an opening which extendsbetween the first and second end surfaces 176 and 178 in a directionparallel to the planar outer side surface 162 of the second plate 32.The second rod passage 182 extends parallel to and has the same diameteras first rod passage 180. The second rod passage 182 is defined by acylindrical surface 185 and tapered pilot surfaces 186 and 187 atopposite ends of the cylindrical surface 185. The diameter of thecylindrical surface 185 is slightly greater than the diameter of thesecond rod 14.

A circular first fastener opening 190 extends through the centralportion 166 of the second plate 32. The first fastener opening 190 hasan axis 192 (FIGS. 2 and 4) which extends perpendicular to the plane ofthe outer side surface 162 of the second plate 32. The axis 192 extendsin the first direction 94 when the second plate 32 is mounted on thesecond vertebra V2.

The first fastener opening 190 is partially defined by a larger diametercylindrical surface 196 (FIG. 8) which extends from the outer sidesurface 162 of the second plate 32 in a direction into the material ofthe central portion 166 of the second plate. The cylindrical surface 196is centered on the axis 192 of the first fastener opening 190. The firstfastener opening 190 is partially defined by a smaller diametercylindrical surface 198 which extends from the inner side surface 164 ofthe second plate 210 in a direction into the material of the centralportion 166 of the second plate, to a location spaced radially inwardfrom the surface 196. The cylindrical surface 198 is centered on theaxis 192 of the first fastener opening 190.

An annular shoulder surface 200 (FIGS. 2 and 8) extends radially(relative to the axis 192) between the cylindrical surfaces 196 and 198.The shoulder surface 200 and the larger diameter cylindrical surface 196define a recess 202 in the outer side surface 162 of the second plate32.

The main body portion 160 of the second plate 32 also includes acircular second fastener opening 210 formed at a location adjacent toand intersecting the first rod passage 180 in the first side portion 168of the second plate. The second fastener opening 210 extends throughboth the second end surface 178 of the second plate 32 and the outerside surface 162 of the second plate.

The second fastener opening 210 is partially defined by a largerdiameter cylindrical surface 212 (FIG. 8) which extends from the outerside surface 262 of the second plate 32 in a direction into the materialof the first side portion 168 of the second plate. The cylindricalsurface 212 is centered on an axis 214 (FIGS. 2 and 4) of the secondfastener opening 210. The cylindrical surface 212 intersects thecylindrical surface 181 which defines the first rod passage 180. Thus,the second fastener opening 210 overlaps a portion of the first rodpassage 180.

The second fastener opening 210 is partially defined by a smallerdiameter cylindrical surface 216 which extends from the inner sidesurface 264 of the second plate 32 in a direction into the material ofthe first side portion 168 of the second plate, to a location spacedradially inward from the surface 212. The cylindrical surface 216 iscentered on the axis 214 of the second fastener opening 210.

An annular shoulder surface 218 (FIGS. 4 and 8) extends radially(relative to the axis 214) between the cylindrical surfaces 212 and 216.The shoulder surface 218 and the larger diameter cylindrical surface 212define a recess 220 in the outer side surface 262 of the second plate32.

The axis 214 of the second fastener opening 210 extends transverse tothe axis 192 of the first fastener opening 190. Specifically, the axis214 of the second fastener opening 210 converges with the axis 192 ofthe first fastener opening 190 as viewed in a transverse plane at rightangles to the vertical axis A, as can be seen from FIG. 4. In theillustrated embodiment, the axis 214 converges with the axis 192 atangle of about 100 as viewed in this transverse plane.

The axis 214 of the second fastener opening 210 also converges with theaxis 192 of the first fastener opening 190 as viewed in the sagittalplane, as can be seen in FIG. 2. In the illustrated embodiment, the axis214 converges with the axis 192 at an angle of 45° as viewed in thesagittal plane. It is contemplated that this angle of convergence couldbe in the range of from about 30° to about 60° as viewed in the sagittalplane.

The main body portion 160 of the second plate 32 also includes acircular third fastener opening 230 formed at a location adjacent to andintersecting the second rod passage 182 in the second side portion 170of the second plate. The third fastener opening 230 extends through boththe second end surface 178 of the second plate 32 and the outer sidesurface 162 of the second plate. The distance between the third fasteneropening 230 in the second plate 32 and the second fastener opening 210in the second plate is slightly less than the distance between the thirdfastener opening 130 in the first plate 30 and the second fasteneropening 110 in the first plate.

The third fastener opening 230 is partially defined by a larger diametercylindrical surface 232 (FIG. 8) which extends from the outer sidesurface 262 of the second plate 32 in a direction into the material ofthe second side portion 170 of the second plate. The cylindrical surface232 is centered on an axis 234 (FIG. 4) of the third fastener opening230. The cylindrical surface 232 intersects the cylindrical surface 185which defines the second rod passage 182. Thus, the third fasteneropening 230 overlaps a portion of the second rod passage 182.

The third fastener opening 230 is partially defined by a smallerdiameter cylindrical surface 236 (FIG. 8) which extends from the innerside surface 264 of the second plate 32 into the material of the secondside portion 170 of the second plate to a location spaced radiallyinward from the surface 232. The cylindrical surface 236 is centered onthe axis 234 of the third fastener opening 230.

An annular shoulder surface 238 (FIGS. 4 and 8) extends radially(relative to the axis 234) between the cylindrical surfaces 232 and 236.The shoulder surface 238 and the larger diameter cylindrical surface 232define a recess 240 in the outer side surface 162 of the second plate32.

The axis 234 of the third fastener opening 230 is coplanar with the axis214 of the second fastener opening 210. The axis 234 of the thirdfastener opening 230 extends transverse to the axis 192 of the firstfastener opening 190. Specifically, the axis 234 of the third fasteneropening 230 converges with the axis 192 of the first fastener opening190 as viewed in a transverse plane at right angles to the vertical axisA, as can be seen from FIG. 4. In the illustrated embodiment, the axis234 converges with the axis 192 at an angle of about 10° as viewed inthis transverse plane.

The axis 234 of the third fastener opening 230 also converges with theaxis 192 of the first fastener opening 190 as viewed in the sagittalplane, as can be seen from FIG. 2. In the illustrated embodiment, theaxis 234 converges with the axis 192 at an angle of 45°. It iscontemplated that this angle of convergence as viewed in the sagittalplane could be in the range of from about 30° to about 60°.

The second plate 32 includes a lip portion or lip 250 which is formed asone piece with the main body portion 160 of the second plate. The lip250, best seen in FIGS. 4 and 7, projects from the second end portion174 of the main body portion 160 of the second plate 32. The lip 250projects in the first direction 94 (FIG. 2) when the second plate 32 ismounted on the second vertebra V2.

The lip 250 has a planar configuration as viewed in the first direction94, for example, as seen in FIG. 2. The lip 250, as viewed in adirection parallel to the plane of the outer side surface 162 of thesecond plate 32, has an arcuate configuration generally following thearcuate configuration of the inner side surface 164 of the main bodyportion 160 of the second plate 32. The lip 250 extends continuouslybetween the first and second side portions 168 and 170 of the secondplate 32. Alternatively, the lip 250 may be discontinuous at one or morelocations along the width of the second plate 32.

The lip 250 has an outer end surface 252 (FIG. 2) which is formed as anextension of the second end surface 178 of the main body portion 160 ofthe second plate 32. An opposite inner end surface 254 (FIGS. 2 and 8)of the lip 250 extends parallel to the outer side surface 252. The lip250 also has an inner side surface 256 which extends between the innerand outer end surfaces 252 and 254 of the lip 250. The second and thirdfastener openings 210 and 230 extend partially through the lip 250. Thesecond fastener opening 210, as well as the third fastener opening 230,extend through the corner between, or intersection of, the lip 250 andthe main body portion 160 of the second plate 32.

The fasteners 38, 40, 42, 44, 46, and 48, which connect the first plate30 with the first vertebra V1 and the second plate 32 with the secondvertebra V2, are identical to each other. Because the fasteners 38-48are identical, only the fastener 40 is described herein in detail.

The fastener 40 (FIG. 3) includes a sleeve 300 and an expander 310. Thesleeve 300 has a hollow, elongate shank portion 302 centered on alongitudinal central axis 304 of the fastener 40. The shank portion 302defines a cylindrical central opening 308 in the sleeve 300. A coarseexternal helical thread convolution 306 is formed on the outerperipheral surface of the shank portion 302 of the sleeve 300.

The shank portion 302 of the sleeve 300 is radially and axially slottedso that the shank portion is expandable radially. A series ofprojections (not shown) are formed on the inner surface of the sleeve300 for engagement by the expander 310 to expand the shank portion 302of the sleeve in a manner described below.

A head end portion 314 of the sleeve 300 has a cylindrical outer sidesurface 316. An annular lip or rim 318 extends around the head endportion 314 of the sleeve 300 and projects radially outward from theouter side surface 316. The head end portion 314 of the sleeve 300 has aconical inner side surface 320 and a conical inner side surface 322. Theconical inner side surface 322 merges with an internal threadconvolution 324 formed on the sleeve 300.

The head end portion 314 of the sleeve 300 is radially and axiallyslotted to define four segments 326 of the head end portion. The foursegments 326 are movable radially relative to each other and to the axis304 of the fastener 40 so that the head end portion 314 of the sleeve300 is expandable radially.

The expander 310 has a head end portion 340 and a shank portion 342. Aninner end 344 of the shank portion 342 of the expander 310 is slightlylarger in diameter than the cylindrical central opening 308 in thesleeve 300.

The head end portion 340 of the expander 310 has an X-shaped driver slot346 for receiving a driving tool for rotating the expander relative tothe sleeve 300. The head end portion 340 has a conical outer sidesurface 348 and a conical outer side surface 350. The conical outer sidesurface 350 on the head end portion 340 of the expander 310 has adifferent angle of taper than does the conical inner side surface 322 onthe head end portion 314 of the sleeve 300.

The conical outer side surface 350 on the head end portion 340 of theexpander 310 merges with an external thread convolution 352 formed onthe expander 310. The external thread convolution 352 on the expander310 screws into the internal thread convolution 324 on the sleeve 300.

To install the apparatus 10 on the spinal column C, the rods 12 and 14are first assembled with the plates 30 and 32. Specifically, the firstrod 12 is inserted through the first rod passage 80 in the first plate30 and through the first rod passage 180 in the second plate 32. One ofthe tapered pilot surfaces 83 and 84 on the first plate 30, and one ofthe tapered pilot surfaces 183 and 184 on the second plate 32, guideinsertion of the first rod 12. The second rod 14 is inserted through thesecond rod passage 82 in the first plate 30 and through the second rodpassage 182 in the second plate 32. One of the tapered pilot surfaces 86and 87 on the first plate 30, and one of the tapered pilot surfaces 186and 187 on the second plate 32, guide insertion of the second rod 14.

The assembly of the rods 12 and 14 and the plates 30 and 32 is thenpositioned over the exposed anterior surface of the spinal column C. Thefirst plate 30 (FIG. 2) is positioned adjacent to the first vertebra V1so that the first end surface 154 on the lip 150 of the first plateengages a lower surface 360 on the first vertebra V1. The lower surface360 on the first vertebra V1 faces toward the second vertebra V2. Thesecond plate 32 is positioned adjacent to the second vertebra V2 so thatthe first end surface 254 on the lip 250 of the second plate engages anupper surface 362 on the second vertebra V2. The upper surface 362 onthe second vertebra V2 faces toward the first vertebra V1.

With the first plate 30 on the first vertebra V1, and the second plate32 on the second vertebra V2, a suitable drill guide and drill (notshown) are used to drill fastener openings in the first vertebra V1 andin the second vertebra V2.

The fasteners 38, 40 and 42 are inserted to connect the first plate 30with the first vertebra. The insertion and securing of the fastener 40,although not necessarily performed first, will be described asexemplary.

The sleeve 300 of the fastener 40 is inserted through the secondfastener opening 110 in the first plate 30. The sleeve 300 of thefastener 40 is threaded into the drilled opening in the vertebra V1 in aknown manner (not shown) to fix the sleeve in position in the vertebraV1. The unexpanded head portion 314 of the sleeve 300 is disposed in therecess 120 in the first plate 30.

The expander 310 of the fastener 40 is then inserted into the sleeve300. The externally threaded portion 352 of the expander 310 is screwedinto the internal threads 324 on the sleeve 300. When the expander 310is fully screwed into the sleeve 300, the inner end portion 344 of theexpander 310 causes the shank portion 302 of the sleeve to expandradially outward, helping to lock the sleeve in place in the vertebraV1. When the expander 310 is fully screwed into the sleeve 300, the headportion 340 of the expander 310 engages the head portion 314 of thesleeve 300. The head portion 340 of the expander 310 wedges the lockingsegments 326 on the sleeve 300 radially outward into engagement with thefirst plate 30 to rigidly lock the fastener 40 in position relative tothe first plate. The head of the fastener 40 is adjacent to the lip 150.

The remaining fasteners 38 and 42 for the first plate 30 are similarlysecured to the vertebra V1 and are rigidly locked to the first plate.The heads of the fasteners 38 and 42 are adjacent to the lip 150. As aresult, the first plate 30 is securely connected with the first vertebraV1.

The fasteners 44, 46 and 48 are similarly used to connect the secondvertebra V2 and the second plate 32. The heads of the fasteners 44, 46,and 48 are adjacent to the lip 250. As a result, the fasteners 44, 46and 48 are rigidly locked to the plate 32 and the plate 32 is securelyconnected with the second vertebra V2.

As can be seen in FIG. 2, the fastener 40 (as well as the fastener 42,not shown in FIG. 2) extends at an angle (upward as viewed in FIG. 2) tothe lip 150. Accordingly, when the fasteners 40 and 42 are tightenedinto the first vertebra V1, the fasteners tend to draw the lip 150 ofthe first plate 30 tightly against the surface 360 of the vertebra, thatis, in an upward direction as viewed in FIG. 2. At the same time, thefasteners 40 and 42, as well as the fastener 38, tend to draw the mainbody portion 60 of the first plate 30 tightly against the anteriorsurface of the first vertebra V1, that is, in a direction to the left asviewed in FIG. 2. Accordingly, it can be seen that tightening thefasteners 38, 40 and 42 tends to draw the first plate 30 in twodirections against the first vertebra V1.

The first fastener 38 has a longitudinal central axis which iscoincident with the axis 92 of the first fastener opening 90 when thefirst fastener 38 is disposed in the first fastener opening 90 in thefirst plate 30. When the second fastener 40 is disposed in the secondfastener opening 110 in the first plate 30, the longitudinal centralaxis 304 of the second fastener 40 is coincident with the axis 114 ofthe second fastener opening 110.

As described above, the axis 92 of the first fastener opening 90 and theaxis 114 of the second fastener opening 110 converge at an acute angleas viewed in the sagittal plane (FIG. 2). Therefore, the longitudinalaxis of the first fastener 38 and the longitudinal axis 304 of thesecond fastener 40 converge at an acute angle as viewed in the sagittalplane (FIG. 2) when the first and second fasteners 38 and 40 connect thefirst plate 30 with the first vertebra V1. In the illustratedembodiment, the axis of the first fastener 38 and the axis 304 of thesecond fastener 40 converge at an angle of about 45° as viewed in thesagittal plane. It is contemplated that this angle of convergence in thesagittal plane could be in the range of from about 30° to about 60°.

When the third fastener 42 is disposed in the third fastener opening 130in the first plate 30, the longitudinal central axis of the thirdfastener 42 is coincident with the axis 134 of the third fasteneropening 130. As described above, the axis 92 of the first fasteneropening 90 and the axis 134 of the third fastener opening 110 convergeat an acute angle as viewed in the sagittal plane (FIG. 2). Therefore,the longitudinal axis of the first fastener 38 and the longitudinal axisof the third fastener 42 converge at an acute angle as viewed in thesagittal plane (FIG. 2) when the first and third fasteners 38 and 42connect the first plate 30 with the first vertebra V1. In theillustrated embodiment, the axis of the first fastener 38 and the axisof the third fastener 42 converge at an angle of about 45° as viewed inthe sagittal plane. It is contemplated that this angle of convergence inthe sagittal plane could be in the range of from about 30° to about 60°.

The second plate 32 is, in a similar manner, secured in positionrelative to the second vertebra V2. Tightening the fasteners 44, 46 and48 tends to draw the second plate 32 in two directions against thesecond vertebra V2.

When the first fastener 44, the second fastener 46, and the thirdfastener 48 connect the second plate 32 with the second vertebra V2, theaxis of the first fastener 44 and the axis of the second fastener 46converge at an acute angle as viewed in the sagittal plane (FIG. 2).Also, the axis of the first fastener 44 and the axis of the thirdfastener 48 converge at an acute angle as viewed in the sagittal plane(FIG. 2). In the illustrated embodiment, these axes converge at an angleof about 45° as viewed in the sagittal plane. It is contemplated thatthis angle of convergence in the sagittal plane could be in the range offrom about 30° to about 60°.

The fact that there are three screws which secure each one of the plates30 and 32 to the spinal column C also helps to maintain proper placementof the plates. These features help the apparatus 10 maintain thevertebrae V1 and V2 in place when the cervical spine is subjected tovarious degrees of motion of the human head.

When the second plate 32 is being connected with the second vertebra V2,the outer fasteners 46 and 48 secure the second plate and the secondvertebra. The fasteners 46 and 48 also serve to interlock the secondplate 32 with the rods 12 and 14. This is because the locking segments326 on the sleeves 300 of the fasteners 46 and 48 (FIG. 4) move radiallyoutward into engagement with the rods 12 and 14, respectively, when eachfastener's expander is fully screwed into the fastener's sleeve. Theengagement between the fasteners 46 and 48 and the rods 12 and 14 blocksmovement of the fasteners 46 and 48 relative to the rods. The radialmovement of the locking segments 326 of the fasteners also causes therods to be clamped against the cylindrical surfaces 181 and 185 whichdefine the rod passages 180 and 182, respectively in the second plate32. As a result, the expanded fasteners 46 and 48 block movement of thesecond plate relative to the rods 12 and 14.

The first plate 30, in contrast, is movable relative to the rods 12 and14, because the second and third fastener openings 110 and 130 arespaced apart from the rod passages 80 and 82. Therefore, the first plate30 is movable relative to the second plate 32.

Accordingly, the first vertebra V1 is movable vertically downwardrelative to the second vertebra V2. This relative movement allows forthe maintaining of a load on bone graft placed between the vertebrae V1and V2. If the first plate 30 were not movable vertically downwardrelative to the second plate 32, then the distance between the vertebraeV1 and V2 would be fixed. If bone graft were placed between thevertebrae V1 and V2 and the bone graft resorbed sufficiently, the bonegraft could possibly shrink out of engagement with one or both of thevertebrae V1 and V2. Allowing relative movement of the plates 30 and 32can help to maintain a desired load on bone graft placed between thevertebrae V1 and V2 and maintains the vertebrae in contact with the bonegraft to facilitate bone growth. The lips 150 and 250 on the plates 30and 32 are, preferably, configured so that the lips do not contact bonegraft placed between the vertebrae.

The caps 50 and 54 on the rods 12 and 14, respectively, limit movementof the first vertebra V1 in a direction away from the second vertebraV2. This helps to maintain a load on the bone graft and maintain thevertebrae V1 and V2 in contact with the bone graft.

It may not be necessary or desirable, in some circumstances, to use adynamic (movable) plate such as the plate 30. In such circumstances, twolocking plates identical to the plate 32 can be used in the sameapparatus 10. Such a system is illustrated in FIG. 9. The upper plate 32(FIG. 9) is fixed in position relative to the vertebra V1 and to therods 12 and 14. The lower plate 32 (FIG. 9) is fixed in positionrelative to the vertebra V2 and to the rods 12 and 14. Accordingly, theapparatus 10 (FIG. 9) blocks relative movement between the vertebrae V1and V2.

FIGS. 10 and 11 illustrate a plate 30 a which is constructed inaccordance with a second embodiment of the present invention. The plate30 a can be substituted, in the apparatus 10, for the plate 30. Theplate 30 a is generally similar to the plate 30 (FIGS. 5 and 6), andsimilar reference numerals are used to designate similar parts, with thesuffix “a” added in FIGS. 10 and 11 for clarity.

In the plate 30 a, a pair of set screws 370 are provided for engagingthe rods 12 and 14 to block movement of the plate, and thereby itsassociated bone portion, relative to the rods. Specifically, the outerside surface 62 a of the plate 30 a is recessed at 372 adjacent to thesecond rod passage 82 a. A seat 374 extends inwardly from the recess 372to a threaded opening 376. An inner end portion 378 of the opening 376intersects with the second rod passage 82 a. On the opposite sideportion 68 a of the plate 30 a, a second threaded opening 380 intersectsthe first rod passage 80 a.

After the plate 30 a is assembled with the rods 12 and 14 and positionedadjacent to the spinal column C, fasteners such as the fasteners 38-42are inserted through fastener openings 90 a, 110 a, and 130 a in theplate 30 a, to secure the plate to its associated bone portion. The headend portions of the fasteners for the plate 30 a do not engage the rods12 and 14, and do not clamp the rods against the plate 30 a.

A set screw 370 is threaded into the opening 376. An inner end portion382 of the set screw 370 engages the cylindrical outer surface of thesecond rod 14. The engagement of the set screw 370 with the second rod14 clamps the rod against the second side portion 70 a of the plate 30a. Another set screw 370 is threaded into the opening 380 to engage thefirst rod 12 and clamp the first rod against the first side portion 68 aof the plate 30 a.

As a result, the set screws 370, the rods 12 and 14, and the plate 30 aare interlocked. The plate 30 a is movable relative to (along the lengthof) the rods 12 and 14. Because the plate 30 a is fixed to itsassociated bone portion, then the bone portion also is movable relativeto the rods 12 and 14.

In the plate 30 a, a portion of the lip 150 a is removed at the locationof the fastener openings 110 a and 130 a, to provide better visibility.This provides two lip segments 151 and 153 at the side portions 68 a and70 a, respectively, of the plate 30 a. The lip segments 151 and 153 arespaced apart on opposite sides of the longitudinal axis, or centerline,of the plate 30 a. A portion of the lip 150 a also is removed at thelateral center of the plate 30 a, and a notch 384 is provided in theplate 30 a, again to increase visibility.

From the above description of the invention, those skilled in the artwill perceive improvements, changes and modifications in the invention.Such improvements, changes and modifications within the skill of the artare intended to be covered by the appended claims.

Having described the invention, we claim:
 1. An apparatus for use inretaining a first vertebra of a spinal column in a desired spatialrelationship with a second vertebra of the spinal column with a graftbetween the vertebra, said apparatus comprising: a plate adapted to befastened to the first vertebra, the plate including a body and a lipprojecting from the body, the lip being adapted to engage a surface ofthe first vertebra that faces toward the second vertebra and to remainspaced apart from the graft, a substantially rigid member positionablealong the spinal column coupled to the plate.
 2. The apparatus of claim1, wherein: the plate is formed to include a first end and a second end,and the lip projects from the second end.
 3. The apparatus of claim 1,wherein the body includes an outer side surface and the lip extends fromthe plate generally transverse to the outer side surface.
 4. Theapparatus of claim 3, wherein the outer side surface is generallyplanar.
 5. The apparatus of claim 1, wherein the body is formed toinclude first and second openings.
 6. The apparatus of claim 5, furthercomprising a first fastener extendable through the first opening tocouple the body to the first vertebra, the first fastener having a firstlongitudinal axis.
 7. The apparatus of claim 6, further comprising asecond fastener extendable through the second opening to couple the bodyto the first vertebra, the second fastener having a second longitudinalaxis.
 8. The apparatus of claim 1, wherein the plate is adapted tofasten to the second vertebra.
 9. An apparatus for use in retaining afirst vertebra of a spinal column in a desired spatial relationship witha second vertebra of the spinal column with a graft between thevertebra, said apparatus comprising: a plate adapted to be fastened tothe first vertebra, the plate including a body and a lip projecting fromthe body, the lip being adapted to engage a surface of the firstvertebra that faces toward the second vertebra and to remain spacedapart from the graft, wherein the body includes first and second sidesand the lip has a first segment adjacent to the first side and a secondsegment adjacent to the second side.
 10. The apparatus of claim 9,wherein the lip extends substantially continuously along the bodybetween the first and second sides.
 11. An apparatus for use inretaining a first vertebra of the spinal column in a desired spatialrelationship with the second vertebra of the spinal column with a graftbetween the vertebra, said apparatus comprising: a plate adapted to befastened with the vertebra, the plate including a body and a lipprojecting from the body, the lip being adapted to engage a surface ofthe first vertebra, face toward the second vertebra, and extend aroundthe graft; the body being formed to include first and second openings; afirst fastener extendable through the first opening to couple the bodywith the first vertebra, the first fastener having a first longitudinalaxis; and a second fastener extendable through the second opening tocouple the body to the first vertebra, the second fastener having asecond longitudinal axis; the first longitudinal axis and the secondlongitudinal axis converging at an acute angle.
 12. An apparatus for usein retaining a first vertebra of a spinal column in a desired spatialrelationship with a second vertebra of the spinal column with a graftbetween the vertebra, said apparatus comprising: a substantially rigidmember positionable along the spinal column, and a plate coupled to thesubstantially rigid member and adapted to be fastened with the firstvertebra, the plate being formed to include a body and a lip projectingfrom the body and being adapted to engage a surface of the firstvertebra.
 13. The apparatus of claim 12, wherein the body includes acorner defined by a first outer surface and a second outer surfaceextending from the first outer surface, the body further including firstand second openings extending through the corner.
 14. The apparatus ofclaim 12, wherein the body has first and second sides and the lip has afirst segment adjacent to the first side.
 15. The apparatus of claim 12,wherein the body includes a first end aid a second end disposedintermediate the first end and the second vertebra the body furtherincluding first and second openings disposed in the second end.
 16. Theapparatus of claim 12, wherein a corner defined by a first outer surfaceand a second outer surface extending from the first outer surface, thebody further including first and second openings through the corner. 17.The apparatus of claim 16, further comprising a first fastener formedfor extension through the first opening into the first vertebra and asecond fastener formed for extension through the second opening into thesecond vertebra.
 18. An apparatus for use in retaining a first vertebraof a spinal column in a desired spatial relationship with the secondvertebra of the spinal column with a graft between the vertebra, saidapparatus comprising: a longitudinal member positionable along thespinal column; a plate coupled to the longitudinal member and adapted tobe fastened with the first vertebra, the plate being formed to include abody and a lip projecting from the body and being adapted to engage asurface of the first vertebra; the body including first and second sidesand the lip including a first segment adjacent to the first side; thelip including a second segment adjacent to the second side.
 19. Theapparatus of claim 18, wherein the lip extends substantiallycontinuously along an edge between the first and second sides.
 20. Anapparatus for use in retaining a first vertebra of a spinal column in adesired spatial relationship with a second vertebra of the spinal columnwith a graft between the vertebra, said apparatus comprising: a plateadapted to be fastened to the first vertebra, the plate including a bodyformed to include an opening therethrough and a lip projecting from thebody, the lip being adapted to engage a surface of the first vertebra, afastener formed for extension through the opening into the firstvertebra; and a substantially rigid member positionable along the spinalcolumn coupled to the plate.
 21. The apparatus of claim 20, wherein thebody has first and second ends and the opening is formed adjacent to thesecond end.
 22. The apparatus of claim 21, wherein the lip projects fromthe second end of the body.
 23. An apparatus for use in retaining afirst vertebra of a spinal column in a desired spatial relationship witha second vertebra of the spinal column with a graft between thevertebra, said apparatus comprising: a plate adapted to be fastened withthe first vertebra, the plate including a body formed to include anopening therethrough and a lip projecting from the body, the lip beingadapted to engage a surface of the first vertebra; and a fastener formedfor extension through the opening into the first vertebra; the bodyhaving first and second ends and the opening being formed adjacent tothe second end; the lip projecting from the second end of the body; thebody including first and second sides and the lip extending between thefirst and second sides.